(Meth)acrylic resin compositions have excellent transparency and low optical distortion and are therefore used in production of optical members such as lenses, prisms, retardation films, light guide plates, light diffuser films, polarizer plate protective films.
There have been developed various methods for producing (meth)acrylic resin compositions for optical members. For example, Patent Document 1 discloses a method comprising continuously feeding a recycled liquid containing a monomer component mainly comprised of unreacted methyl methacrylate recovered after polymerization as well as a monomer component mainly comprised of fresh methyl methacrylate to a distillation column, continuously feeding the resulting distilled monomer components into a polymerization reactor for bulk polymerization, subsequently devolatizing the resulting liquid containing a polymerization product to recover the polymerization product and simultaneously recovering as unreacted monomer for use as the recycled liquid, and feeding a solvent having a boiling point higher than the boiling points of the monomers to the bottom of the distillation column and simultaneously discharging, from the bottom, a liquid in the same amount as that of the solvent being fed.
Patent Document 2 discloses a method comprising continuously feeding a monomer component mainly comprised of methyl methacrylate to a polymerization reactor for bulk polymerization, subsequently devolatizing the resulting liquid containing a polymerization product to recover the polymerization product and simultaneously recovering an unreacted monomer for recycling, and removing an acidic substance present in the system by using a basic anionic exchange resin.
Patent Document 3 discloses a method comprising continuously feeding a monomer component mainly comprised of methyl methacrylate to a polymerization reactor for bulk polymerization, subsequently conducting devolatizing treatment of the resulting liquid containing a polymerization product to separate an unreacted monomer, introducing the separated unreacted monomer to a distillation column, and conducting distillation under reduced pressure so that the content of methyl methacrylate dimer reaches 0.1 to 1.0% by mass to recover the monomer.